1. Field of the Invention
The present invention relates to a method for producing a hydrogen-containing fluorinated hydrocarbon and an apparatus therefor. It is to be noted that throughout the present specification, the term "hydrogen-containing fluorinated hydrocarbon" means a compound as a hydrocarbon of which a part (i.e. one or more) of hydrogen atoms is substituted by a fluorine atom(s) and which contains at least one hydrogen atom. The hydrogen-containing fluorinated hydrocarbon may or may not contain a chlorine atom(s). In terms of example, the hydrogen-containing fluorinated hydrocarbon includes a hydrogen-containing fluorinated alkane and a hydrogen-containing fluorinated alkene and the like.
2. Description of the Related Art
A chlorofluorocarbon generally known as a flon gas has been used for a foaming agent, a cleaning agent, and a refrigerant owing to its stable and thermal properties. The chlorofluorocarbon is a simple alkane such as methane or ethane of which all of hydrogen atoms are substituted by a chlorine atom(s) and/or a fluorine atom(s). Recently, such a chlorofluorocarbon has been subjected to regulation since the chlorofluorocarbon has been found to have a property of damaging the ozone layer.
Thus, demand of a hydrogen-containing fluorinated hydrocarbon which scarcely affects or does not affect the ozone layer has been increased and the development of such hydrogen-containing fluorinated hydrocarbon has been undertaken. The hydrogen-containing fluorinated hydrocarbon includes a hydrogen-containing fluorinated alkane, for example, 2,2-dichloro-1,1,1-trifluoroethane (also called as HCFC-123) and 1,1,1,3,3-pentafluoropropane (also called as HFC-245fa). HCFC-123 is a useful compound as a refrigerant for a turbo refrigerator or as an intermediate raw material for the production of 2-chloro-1,1,1,2-tetrafluoroethane (also called as HCFC-124) and pentafluoroethane (also called as HCFC-125). Further, HFC-245fa is a useful compound for a foaming agent which is not likely to damage the ozone layer.
In order to produce such a hydrogen-containing fluorinated hydrocarbon, the conventional method for producing a chlorofluorocarbon containing no hydrogen atom such as trichlorofluoromethane (also called as CFC-11), dichlorodifluoromethane (also called as CFC-12), and 1,1,2-trichlorotrifluoroethane (also called as CFC-113) can be applicable. As the conventional method for producing the chlorofluorocarbon, a method by reacting a chlorinated alkene and/or a chlorinated alkane with a hydrogen fluoride in the presence of a fluorination catalyst to produce the chlorofluorocarbon is known.
In the foregoing method for producing the chlorofluorocarbon, a reaction mixture has a corrosive property owing to the interaction of the fluorination catalyst and hydrogen fluoride. Upon the application of such a method to the production of the hydrogen-containing fluorinated hydrocarbon, reaction conditions result is a reaction mixture which shows an extremely intense corrosive property. Consequently, if a conventional and commonly used apparatus material, e.g. a stainless steel based material, is used for a reactor in which a fluorination reaction is to be carried out to produce the hydrogen-containing fluorinated hydrocarbon, the reactor will be severely corroded and worn-out. Therefore, there occur problems of a shorter lifetime of the reactor and an increased facility cost including a cost of the reactor.
Taking the high corrosive property of the reaction mixture into consideration, it is suggested that the following reactors are employed for the fluorination reaction:
(1) A reactor made of a composite material which contains at least one corrosion resistant metal selected from a group consisting of gold, platinum, palladium, molybdenum, rhenium, and tungsten (see Japanese Patent Kohyo Publication No. 8-501551); PA1 (2) A reactor made of a fluoro resin or lined with a fluoro resin (see Japanese Patent Kokai Publication No. 7-233102); PA1 (3) A reactor having an inner surface made of a corrosion resistant metal material containing aluminum (see Japanese Patent Kokai Publication No. 10-120602); and PA1 (4) A reactor installed in the inside of a container made of a metal material and at least of which inner surface is coated with a fluoro resin (see WO 99/26720). PA1 (a) supplying one of the reaction raw material (it may be also called as the first reaction raw material) to a gap between an inner reactor made of a material (for example, a certain metal material) which is substantially resistant to the reaction and an outer container made of a material (for example, another certain metal material which may be the same as said certain metal material) which is substantially resistant to at least said one of the reaction raw materials and which is installed outside the inner reactor; PA1 (b) supplying said one of the reaction raw materials (or the first reaction raw material) to the inner reactor; PA1 (c) supplying the other reaction raw material (it may be also called as the second reaction raw material) to the inner reactor; and PA1 (d) reacting said one of the reaction raw materials (or the first reaction raw material) with the other reaction raw material (or the second reaction raw material) in the presence of the fluorination catalyst in the inner reactor so as to obtain the reaction product comprising the hydrogen-containing fluorinated hydrocarbon. According to the present invention, the foregoing object is achieved. In the method of the present invention, the first reaction raw material may be supplied to the inner reactor, for example, through the gap containing the first reaction raw material or directly from a supply source of the first reaction raw material, which will be explained later with reference to FIG. 1.
However, all of the above described reactors (1) to (4) have defects and they are not necessarily optimum for the reactor to be employed for producing the hydrogen-containing fluorinated hydrocarbon. Particularly, among the corrosion resistant metals to be used for the reactor (1), gold, platinum, palladium and rhenium are too expensive to be used for producing a large scale reactor. Molybdenum and tungsten have a disadvantage of insufficient mechanical strength since welded parts of such metals are very brittle on account of welding heat and a trace amount of a contaminant which is introduced into the parts on welding. In addition, molybdenum and tungsten are inherently hard and brittle metal materials, and thus have inferior workability. Therefore, it is substantially impossible to form an industrial scale reactor employing these materials.
In the case of using a resin material like as in the reactors (2) and (4), since the resin materials generally have low thermal conductivity as compared with metal materials, the resin materials make it very difficult to sufficiently transfer a necessary quantity of heat from outside of the reactor to the inside of the reactor in order to gasify a reaction product, and especially in the case of using such a reactor having a large capacity, it is difficult to control a reaction temperature.
In the case of the reactor (3), though it has high corrosion resistance in a water-free condition, corrosion considerably proceeds even when only a small amount of water is present in the reaction mixture, so that it makes maintenance of the reactor extremely difficult, for example, water-washing which may leave water in the reactor can not be employed for periodic maintenance.